From 9a7420ccd05395af34cced848a6f181a34e6b495 Mon Sep 17 00:00:00 2001
From: Jeremy Ashkenas <jashkenas@gmail.com>
Date: Sat, 8 May 2010 12:44:54 -0400
Subject: [PATCH] adding support for calling variadic functions with less than
 the requested number of arguments.

---
 lib/nodes.js            | 14 +++++++++-----
 src/nodes.coffee        | 10 +++++++---
 test/test_splats.coffee | 17 ++++++++++++++++-
 3 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/lib/nodes.js b/lib/nodes.js
index d7542098..f07f6a5c 100644
--- a/lib/nodes.js
+++ b/lib/nodes.js
@@ -1060,8 +1060,9 @@
         if (param instanceof SplatNode && !(typeof splat !== "undefined" && splat !== null)) {
           splat = param;
           splat.index = i;
-          this.body.unshift(splat);
           splat.trailings = [];
+          splat.arglength = this.params.length;
+          this.body.unshift(splat);
         } else if ((typeof splat !== "undefined" && splat !== null)) {
           splat.trailings.push(param);
         } else {
@@ -1153,15 +1154,18 @@
     // Compiling a parameter splat means recovering the parameters that succeed
     // the splat in the parameter list, by slicing the arguments object.
     SplatNode.prototype.compile_param = function compile_param(o) {
-      var _b, _c, len, name, pos, trailing;
+      var _b, _c, idx, len, name, pos, trailing, variadic;
       name = this.name.compile(o);
       o.scope.find(name);
       len = o.scope.free_variable();
       o.scope.assign(len, "arguments.length");
+      variadic = o.scope.free_variable();
+      o.scope.assign(variadic, ("" + len + " >= " + this.arglength));
       _b = this.trailings;
-      for (pos = 0, _c = _b.length; pos < _c; pos++) {
-        trailing = _b[pos];
-        o.scope.assign(trailing.compile(o), ("arguments[" + len + " - " + (this.trailings.length + pos) + "]"));
+      for (idx = 0, _c = _b.length; idx < _c; idx++) {
+        trailing = _b[idx];
+        pos = this.trailings.length - idx;
+        o.scope.assign(trailing.compile(o), ("arguments[" + variadic + " ? " + len + " - " + pos + " : " + (this.index + idx) + "]"));
       }
       return "" + name + " = " + (utility('slice')) + ".call(arguments, " + this.index + ", " + len + " - " + (this.trailings.length) + ")";
     };
diff --git a/src/nodes.coffee b/src/nodes.coffee
index 26552cd2..7061b2ad 100644
--- a/src/nodes.coffee
+++ b/src/nodes.coffee
@@ -773,8 +773,9 @@ exports.CodeNode: class CodeNode extends BaseNode
       if param instanceof SplatNode and not splat?
         splat: param
         splat.index: i
-        @body.unshift(splat)
         splat.trailings: []
+        splat.arglength: @params.length
+        @body.unshift(splat)
       else if splat?
         splat.trailings.push(param)
       else
@@ -830,8 +831,11 @@ exports.SplatNode: class SplatNode extends BaseNode
     o.scope.find name
     len: o.scope.free_variable()
     o.scope.assign len, "arguments.length"
-    for trailing, pos in @trailings
-      o.scope.assign(trailing.compile(o), "arguments[$len - ${@trailings.length + pos}]")
+    variadic: o.scope.free_variable()
+    o.scope.assign variadic, "$len >= $@arglength"
+    for trailing, idx in @trailings
+      pos: @trailings.length - idx
+      o.scope.assign(trailing.compile(o), "arguments[$variadic ? $len - $pos : ${@index + idx}]")
     "$name = ${utility('slice')}.call(arguments, $@index, $len - ${@trailings.length})"
 
   # A compiling a splat as a destructuring assignment means slicing arguments
diff --git a/test/test_splats.coffee b/test/test_splats.coffee
index 00dec887..5b89e773 100644
--- a/test/test_splats.coffee
+++ b/test/test_splats.coffee
@@ -89,4 +89,19 @@ class Child extends Parent
     nums: [3, 2, 1]
     super nums...
 
-ok (new Child()).meth().join(' ') is '3 2 1'
\ No newline at end of file
+ok (new Child()).meth().join(' ') is '3 2 1'
+
+
+# Functions with splats being called with too few arguments.
+pen: null
+method: (first, variable..., penultimate, ultimate) ->
+  pen: penultimate
+
+method 1, 2, 3, 4, 5, 6, 7, 8, 9
+ok pen is 8
+
+method 1, 2, 3
+ok pen is 2
+
+method 1, 2
+ok pen is 2